Supplemental Information to Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Interest Expense Capitalized in Connection with Development Activity	$ 1,998	$ 475
Mortgage Loan Payable Assumed in Conjunction with a Property Acquisition	0	12,026
Write-off of Fully Depreciated Assets	(36,010)	(27,754)
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Distribution Payable	11,801
Exchange of Operating Partnership Units for Common Stock:
Conversion of Units to Common Stock	0	0
Noncontrolling Interest
Exchange of Operating Partnership Units for Common Stock:
Conversion of Units to Common Stock	(804)	(2,469)
Common Stock
Exchange of Operating Partnership Units for Common Stock:
Conversion of Units to Common Stock	1	3
Additional Paid-in Capital
Exchange of Operating Partnership Units for Common Stock:
Conversion of Units to Common Stock	803	2,466
Common Stock
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Distribution Payable	9,745	0
Preferred Stock
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Distribution Payable	$ 2,056	$ 4,798